Online advertising generates a large amount of online traffic and revenue. Online advertisements are a nearly ubiquitous feature of our online experience because online advertisers typically advertise goods and services on or with websites, mobile apps, video games, set-top boxes, streaming media, and so on. In many cases, advertisements may be targeted to users based on, for example, demographic information, online activities, search activities (e.g., search queries), online shopping activities, and so on. Online advertisements may take the form of one or more pop-up advertisements, pop-under advertisements, banner advertisements, audio advertisements, video advertisements, animated gifs, and so on. Desktop computers, which typically include computer monitors, can offer relatively vast amounts of space for displaying or presenting advertisements. Handheld devices, however, typically provide a limited amount of visual display space or real estate for users to view or interact with, necessarily making online advertisements either annoyingly large, or small and difficult to interact with. When the visual space available for online advertisements is limited, online advertisements may interfere with a user's online experience. For example, a pop-up advertisement may be displayed in such a way that it completely takes over the viewable area of the user's device. As another example, the user may accidentally click on or select the advertisement if the advertisement is displayed over or near a feature of a webpage or application with which the user interacts.